Minor README request: provide link "Quantum Engine"

[mhucka]

The README file at the top level of this repo currently mentions "Quantum Engine" at near the top:

I was trying to learn more about Quantum Engine, and having a little trouble. I think it must be what is mentioned under the heading "Quantum Engine API" here, but am not 100% sure.

To help me and other people coming to this, I'd like to request that the text "Quantum Engine" be hyperlinked to something that would clarify and/or explain more about what it is.

(This is not a critical problem, obviously.)